10

Working in the UCSB Robotics Lab I’ve had the fortune of getting to play with one of those adorable little chewable linux computers , during the ~week before my move to Japan. While unfortunately I wont get to see it though to its installation as the nervous system on a hoping robot, I’ve had the adventure of getting it all up and running with the ROS (Robot Operating System) toolchain. I pulled a bit of hair out during the process, so hopefully this post will prevent others from having to do so.

As of now, this blog describes the process of getting Gumstix to boot Ubuntu Natty from an SD card , autoconnect to wifi, and subscribe to a ROS topic.
I’m using a Gumstix Overo Fire COM, 8GB SD card, and the new Robovero daughter board.

You don’t need that exact hardware, but at minimum:

-Gumstix Overo Air/Fire/FE

-Micro SD card (8 GB in these examples)

-Overo daughter board (could be pretty much any one)

-Computer running Ubuntu

-A wireless (or wired if you have the right Gumstix daughter board) network that both the Overo and Host computer can connect to

Creating the Bootable Ubutnu SD Card

First grab a copy of rootstock – a nifty tool we will use to create our armel ubuntu image:

This is bound to take a while. So in the meantime crack open a new terminal session and get your sd card formatted and bootable by following the directions here. STOP after copying MLO u-boot.bin and uImage to the boot partition, because we will be using our own rootfs image. You can download MLO u-boot.bin and uImage from here.

Once rootstock has completed unzip everything to the SD card’s root partition (lets call it sdroot)

This will also take a while. Make yourself useful by getting your Overo ready for the next step. The Ubuntu image we are building unfortunately does not have built in support for the Overo’s wifi chip, so we are going to swipe the modules and firmware from the nand image (which we know works). You could probably also find this stuff on the interweb , but this way is a pretty simple one stop shop for everything. If your kernel versions do not match you may be better off extracting the stuff from one of the Gumstix images to avoid compadibility issues.

Copying Modules and WiFi Firmware

Plug the daughter board into your desktop as you would normally to get to the serial console, give the boards power and let the Overo boot into the NAND Angstrom distro. We will be connecting to a wifi network to transfer files, becasue afaik there is no reliable way to do this over the serial connection. From the console (in a session thats not extracting files):

If you use encription you are going to have to set up wpa_supplicant.conf , but I’ll trust you know how to do this. The sshd restart probably isnt strictly necessary, but can’t hurt. Also don’t forget your Gumstix’s IP address; lets pretend its 192.168.1.14

Once the files have finished extracting from the SD card you will want to do the following (from a fresh terminal ) :

now I’ll assume you can get your router to statically assign IPs , if not you will have to change things every time your router does. Edit /etc/hosts to include the name of your desktop computer (which will be running roscore) lets pretend your desktop has IP address 192.168.1.4, and you want to name it desky

#echo "192.168.1.4 desky" &gt;&gt; /etc/hosts

#echo "source ~/ros/setup.bash" &gt;&gt; ~/.bashrc

#export ROS_MASTER_URI=http://Desky:11311

. ~/.bashrc

Now ROS is all set up! lets just configure the Gumstix so that it automatically connects to WiFi on boot.

Network Config

You may not need the -4 , but without it my connection would fail every few minutes and I would have to request a new lease.
Also if you are using encryption you will need to set up /etc/wpa_supplicant.conf and change the above lines to something more like:

#ifconfig wlan0 up # wpa_supplicant -Dwext -i wlan0 -c/etc/wpa_supplicant.conf -B
#dhclient wlan0
Now your overo is all set! Unplug the mini-USB and reset the Overo. After about a minute you should see the outermost blue LED blink violently then remain lit. This means you are connected.
To make things easier on ourselves and ROS, lets make another similar entry in /etc/hosts. This time assume the gumstix is 192.168.1.8 and we want to name it gummy

#echo "192.168.1.8 gummy" &gt;&gt; /etc/hosts

no tricks there. Now you can log into your overo wirelessly simply by running

ssh [user]@gummy

You can now run your ROS programs , and the two computers should be able to find each other seamlessly.

09

A recent news article got me thinking about Geiger readings in Japan, after a bit of Googling I came across some cool things like an upcoming Geiger shield from the Tokyo Hackerspace, and an aggregate data feed from Pachube with nearly 500 live datapoints. Excited to have all this data I decided to whip up something simple (in Processing) to plot it all on a map. I’ve been looking into to applying a predictive modeling construct (perhaps something like an ensemble Kalman filter with an atmospheric dispersion model for Cesium 137), to be able to plot the theoretical radiation levels in all of Japan. I tried modeling it simply with exponential decay, but the results were pretty abysmal.. hopefully I’ll hear back from my environmental studies contact and have something legitimately cool to show you shortly.

03

In the not too distant past I was a hardcore Gentoo geek. My computer was MY computer, and its speed and the extent to which it was custom tailored were personal points of pride. Over time more and more of my friends made the switch to Ubuntu, and urged me to follow suit. I resisted.

One day one of these friends challenged me to a boot race and my custom Gentoo kernel was pwnd by a stock Ubuntu build running on [slightly] inferior hardware. So I stopped resisting and agreed to give n00buntu a try.

Not having to untangle circular dependencies or spend hours surfing the forums to get my _____ device working, I’ve have grown increasingly fat, lazy, deaf, dumb, and blind to the inner workings of my system. I’ve become more and more content with the idea that Ubuntu is so fantastical because of black magic pixie dust sprinkled into the source code.

I was reminded again of this boot time wizardry again today while working with a Gumstix Overo board, when a rootstock generated headless Ubuntu build loaded noticeably faster than the Gumstix’s preloaded Angstrom image. Then I came across this forum post titled All about ureadhead :